Lady Sylvia Hermon opposes the link-up between the UUP and Conservatives
The Ulster Unionist Party has selected its party's nominees in all the Northern Ireland Westminster seats except North Down.
UUP North Down MP Lady Sylvia Hermon has said she will not apply to stand for election under the joint Ulster Unionist and Conservative banner.
The candidates have to be considered by a joint Conservative and Unionist committee.
Both the party executives then have to finalise nominations.
In South Belfast, a constituency seen as a target unionist seat, Paula Bradshaw has been selected as the UUP nominee.
In South Antrim, another key Conservative and Unionist seat, Adrian Watson has been selected. Former rugby international Trevor Ringland has been selected to fight East Belfast.
Daphne Trimble is the UUP nominee in Lagan Valley, who will fight the current DUP MP Jeffrey Donaldson.
All these selections are dependent on where the Conservatives want to run their nominees.
The UUP's deadline for nominations in North Down closes at 1700 GMT.
Lady Hermon remains adamant she will not stand under a Conservative banner, but behind the scenes there are ongoing talks aimed at reaching a compromise.
The Ulster Conservatives and Unionists - New Force (UCUNF) electoral link-up between the two parties was forged in 2008.
BBC NI political reporter Stephen Walker said that of all the 18 constituencies in Northern Ireland, North Down has given the Ulster Unionist Party its "biggest headache".
"Lady Hermon has always insisted she is against the electoral alliance with the Tories and won't stand on a joint Conservative and Unionist ticket," he said.
The UUP and Conservatives are to select candidates to stand in Westminster and European elections.
In October, the Conservatives selected Ian Parsley to stand in North Down.
A former Alliance Party member, Mr Parsley joined the Conservative Party in September 2009.
The full list is as follows: North Antrim- Robin Swann; South Antrim- Adrian Watson; East Antrim- Rodney McCune; North Belfast - Fred Cobain; West Belfast- Bill Manwaring; South Belfast- Paula Bradshaw; East Belfast- Trevor Ringland; Strangford- Mike Nesbitt; South Down- John McAllister; Lagan Valley- Daphne Trimble; Upper Bann- Harry Hamilton; Newry and Armagh - Danny Kennedy; Fermanagh and South Tyrone- Tom Elliot; Mid Ulster- Sandra Overend; West Tyrone- Ross Hussey; Foyle- David Harding; East Londonderry- Lesley McAuley.